Well, after upping my project version, this has started happening again.. something I forgot to mention was I deleted the bin/ folder before running the 'Clean' option, but it still isn't fixing it. Hopefully I can track this down.

I wanted to follow up on this in case someone else ran into the problem... sorry if it bumps the post.

This was because I was using a batch file to upload the signed apk, which used command-line ftp - and installing by downloading to the device. I made sure it uploaded in binary. I don't know if it is an issue with overwriting a file or what.. but that is why it was happening.